Field of the Invention
The present invention relates to a magnetic disk drive device, and in particular to control at the time of starting the magnetic disk drive device. More specifically, the invention relates to control of a magnetic disk drive device until the magnetic disk reaches a predetermined speed (until the magnetic disk reaches a rotation-ready state), and control for positioning the magnetic head onto a track constituting an initial position (when the magnetic disk drive device is in the drive-ready state) after the magnetic disk reaches the predetermined speed.
Prior Art
In a magnetic disk drive device of a dedicated servo-method, dedicated servo information required for positioning a magnetic head is written on one surface of a magnetic disk and the servo information is read by a dedicated magnetic head and the servo information read by the magnetic head is used for the positioning of the magnetic head. Data is written in and read from other surfaces by other magnetic heads aligned with the above-mentioned magnetic head for reading the servo information. The magnetic disk drive device of the dedicated servo method has an advantage in that the identification of the track is easy since the servo information can be obtained at all times. A problem associated with this method is that one entire surface of a disk is dedicated for the servo information. This reduces the number of data surfaces which can be used for data recording. This problem is more acute as the number of disks is reduced.
To eliminate this problem, use is made of a magnetic disk drive device of a sector servo (embedded servo) system in which information for positioning is also written on the same surface of the magnetic disk on which data are also written.
There is however increasing demand for further reduction in cost and size of the device and further improvement in the high-speed access. For instance, a Hall-IC (an integrated circuit containing a Hall-element) for producing an index signal which is a one-revolution signal (a signal produced once per revolution) was often built in a spindle motor which rotates the magnetic disk. But recently the trend is to eliminate the Hall-IC to reduce the cost and produce an index signal on the basis of information obtained by reading the disk.
In addition, an access motor for positioning the magnetic heads was provided with a position detector for high-speed access, and a glass slit disk, a light-emitting diode, a photo-transistor, and the like were required for forming an optical encoder of the position detector. The recent trend is again to eliminate these components to reduce the size and to improve the high-access performance, and instead to provide head positioning information written on the magnetic disk in advance, read the positioning information by means of a magnetic head and use it at a control unit for the calculation required for position control.
Thus, the recent magnetic disk drive device has hardware and software configurations different from those of the prior art devices, and various methods of control have been proposed.